CODEWITHSUNDEEP
javascriptgoogle-chromeconsole
Mike Smith
Mike Smith

Reputation: 456

Using external javascript code to run a snippet on the Chrome console

Is it possible in an external javascript code (for example, a userscript through tampermonkey) to run a code snippet on the Chrome console. For example, console.log prints text to the console. Is there some way, like a function console.eval or some more complex way where I can run code on the console without manually opening it on the given website, but using the original javascript code behind the website or a userscript?

Notes: I use Google Chrome on Windows 10. Preferably this answer should be as generally applicable as possible, but first priority for me is for it to work in my environment.

Thanks,

Mike

Upvotes: 1

Views: 485

Answers (1)

The Bomb Squad
The Bomb Squad

Reputation: 4337

Uk, when i said if the page is reloading constantly, the "console" that u think of would also reload??, a lot of us knew about what I'm doing below(if not all of us) but I finally connected it with your question. Using one tab to control the other tab

ONE EDIT: I used an interval to determine if the controlled tab is CLOSED(since a certain value eventually changes if the tab is closed for good)

HOW TO USE:

  1. Open a tab with the same origin as desired url(but not the constantly reloading site)..
    eg: opening a tab on "https://example.com/404" if desired url is "https://example.com" is the desired url(the constantly reloading one)
  2. In the code snippet I have below, you can put your tab controlling code in the loadFn function, where myWindow and this point to the controlled tab's window
    eg: in the loadFn function, myWindow.console.log(1) or this.console.log(1) would both log 1 to the controlled tab's console


SECOND EDIT: I shall explain how it works(and talk about unloadFn as you requested in comments)
I use a combination of unload and load listening to be able to repeatedly send code "on reload" which is not an event in itself so I had to create it. In case I didn't explain myself, I'd go into detail now..
When a page is reloading(or when I'm JUST SPAWNING the page, eg: var myWindow=window.open(desiredUrl)), the unload event happens. There's just one problem however; every time the page is reloading, all event listeners and any code you put is removed(because reload unloads to then reload)
The solution is simple: on every unload, I set the listners again, and since the function would call itself(every time the page unloads), the listeners would successfully be reloaded every time the page reloads(and that is why loadFn could run in the other tab after every reload)
DO NOTE: You might ask "why use a setTimeout then?". Actually it's quite important. Without the setTimeout, the event listeners DO NOT GET ADDED, I think it's because the tab would ignore your commands(since it would be focusing on loading its default stuff(like event listeners for instance)), and asynchronous programming does wonders in this case because it will wait until the other stuff are processed(like event handling stuff) then run
SIDE NOTE: If that's not why setTimeout works and NOT USING it doesn't, all I know is that without it, it doesn't work, and with it, it works


var myWindow=window.open(desiredUrl) //remember to run this code on the same origin as the desiredUrl
function loadFn(){
  //this will happen every time myWindow loads or reloads
  myWindow.alert("It runs in the controlled tab")
  myWindow.console.log("Even in the controlled tab's console it works >:D")
}
function unloadFn(){setTimeout(()=>{
  myWindow.addEventListener('unload',unloadFn)
  myWindow.addEventListener('load',loadFn)
  if(!myWindow.Window){console.warn("myWindow was CLOSED")}
},0)}
myWindow.addEventListener('unload',unloadFn)
//extra thing below to tell if controlled tab is closed >:D
var i=setInterval(()=>{
  //for if controlled tab is closed
  if(!myWindow.document.location){clearInterval(i);console.warn("myWindow was CLOSED")}
},0)

Upvotes: 1

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